Restraint Mechanism for Rotor Blades of a Turbo Engine, an Assembly Method and a Turbo Engine

ABSTRACT

A restraint mechanism for rotor blades of a turbo engine on a rotor disk having blade root receptacles for radial guidance of the rotor blades is disclosed. The restraint mechanism has a plurality of axial securing elements, each having at least one web for positioning in a blade root receptacle, such that each web has a retaining section at one end for establishing a form-fitting design to a mating brace of another axial securing element. A method for axially securing rotor blades on a rotor disk and a turbo engine are also disclosed.

This application claims the priority of European Patent Document No. EP12179777.3, filed Aug. 9, 2012, the disclosure of which is expresslyincorporated by reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a restraint mechanism for rotor bladesof a turbo engine on a rotor disk, a method for axially securing rotorblades on a rotor disk of a turbo engine, and the turbo engine.

Rotor blades 1, which are arranged with their root 2 inserted into anaxial groove 4 of a rotor disk 6 of a turbo engine, as illustrated inFIGS. 1 and 2, are usually secured by a restraint mechanism in the axialdirection. A known restraint mechanism has a plurality of securingelements 8, each of which is arranged in the groove 4 between the root 2and the base of the groove. Each securing element 8 has a web 10 to beplaced in the grooves 4 and has two securing sections 12, 14 extendingaway from the web 10 on the end, becoming wider with respect to thegroove 4, so that, when installed, they are in contact with a front diskarea 16 and a rear disk area 18. Because of the widened securingsections 12, 14 in comparison with the grooves 4, the securing elements8 are positioned in the grooves 4 in front of the blades on the rotordisk 6. However, if a securing section 12, 14 is damaged when bent over,all the blades on the entire rotor disk 6 must be removed to replace thedefective securing element 8. Additional web-type securing elements withwidened securing sections are disclosed in U.S. Patent ApplicationPublication U.S. 2009/0060746 A1 as well as in European PatentApplication EP 1 057 973 A2. Alternative restraint mechanisms alsoprovide curved plate elements which together form a closed ring. Theyare used in the area of the rear disk face between the sections of therotor disk and the blades, each extending over several rotor blades.Such restraint mechanisms are disclosed in European Patent ApplicationEP 0 761 930 A1, German Patent Application DE 199 60 896 A1, U.S. PatentApplication Publication U.S. 2004/0062643 A1 and European PatentApplication EP 1 650 406 A2, for example. One disadvantage of all theseplate-type restraint mechanisms is that corresponding rotor disksections and blade sections are provided for holding the plate elements.In addition, the assembly and dismantling of the individual plateelements to form a closed ring are complex.

The object of the invention is to create a restraint mechanism for rotorblades of a turbo machine on a rotor disk which will eliminate theaforementioned disadvantages and will permit a favorable transfer offorce between the rotor blades and the rotor disk. In addition, anotherobject of the present invention is to create an improved method foraxially securing rotor blades on a rotor disk of a turbo engine as wellas a turbo engine having an improved means of axially securing rotorblades.

A restraint mechanism according to the invention for rotor blades of aturbo engine on a rotor disk having blade root receptacles for placementof the rotor blades has a plurality of axial securing elements, each ofwhich has at least one web for positioning in a blade root receptacle.According to the invention, each web has a retaining section at the endto establish a form-fitting design with a mating brace of an opposingaxial securing element.

Due to the fact that each of the securing elements is connected in aform-fitting manner to the securing element on the opposite side, theyare supported mutually, thereby resulting in a torque-free outwardtransfer of force. Furthermore, a defined flow of force is ensured. Thesecuring elements can be installed from the front or from the rear, asseen in the axial direction, regardless of the direction ofinstallation.

To permit an exchange of the securing elements in the bladed state ofthe rotor disk, the retaining sections may be narrower than the bladeroot receptacles in the area of placement of the securing elements andmay assume an installed position, which is different from a securedposition. When installed, the retaining sections are aligned as flatlyand/or almost as flatly as the webs, so that the retaining sections andthe webs have the same or almost the same height. The retaining sectionsmay be plastically deformable, in which case they are then bent out ofthe flat assembly position into the upright secured position.Alternatively, the retaining sections are prestressed into their uprightsecured position and then can be deformed elastically out of thisposition and into the flat assembly position. In this way, accidentallydamaged securing elements can be replaced at any time, so thatcorresponding repairs can be performed rapidly.

The mating braces are preferably offset in the vertical direction of thesecuring elements and have an elongated shape extending in thetransverse direction of the securing elements, where they have an extentsuch that, when installed, they extend beyond at least one neighboringblade root receptacle and/or they bridge a neighboring blade rootreceptacle. The mating braces are therefore always situated in thesecured position and need not first be moved into this position. Inaddition, the mating braces run onto the rotor disk in assembly and thusdefine a definite axial securing position of the securing elements inthe blade root receptacles.

In a preferred exemplary embodiment, two securing elements form asecuring element pair. Preferred securing elements each have a web fromwhich a mating brace extends on one side in the transverse direction.Each of the two securing elements of this pair has the same, i.e.,identical, L-shaped design. Two neighboring rotor blades can be securedquickly and reliably in this way. The pair of securing elements may beused as a repair part, for example, when a traditional web-type securingelement has been damaged. The defective securing element and aneighboring securing element can be removed and replaced by a pair ofsecuring elements.

However, the restraint mechanism may also have at least one pair ofsecuring elements, such that one securing element has a web with amating brace extending on both sides of the web, while the othersecuring element has two webs spaced a distance apart from one another,connected by a mating brace. When installed, the web of the T-shapedsecuring element is placed between the webs of the U-shaped securingelement, and the retaining sections each form a form-fitting design withthe mating braces. Three neighboring rotor blades can be secured on therotor disk by the U-shaped securing element and the T-shaped securingelement, so that the restraint mechanism may be used with rotor diskshaving an even number of rotor blades or used with rotor disks having anodd number of rotor blades in the combination of the two pairs ofsecuring elements (2 L-shaped securing elements yield one pair ofsecuring elements, 1 T-shaped securing element and 1 U-shaped securingelement yield a pair of securing elements). For example, it isconceivable that the pair of securing elements consisting of theU-shaped securing element and the T-shaped securing element with an oddnumber of rotor blades may be used more or less as the closure of therestraint mechanism.

In another exemplary embodiment, the securing elements do not form aself-contained pair of securing elements but instead identical securingelements are assembled in a chain. Preferred securing elements to formthe securing element chain each have a U-shaped design and have two websjoined together by a mating brace and spaced a distance apart from oneanother, so that two securing elements may be placed with one of theirtwo webs between the webs. Thus each securing element extends over fourrotor blades.

For closing the securing element chain in the case of rotor bladenumbers that are not divisible by four, a U-shaped securing element andan I-shaped securing element may be provided, each being installed oneor more times. Instead of a mating brace, the I-shaped securing elementhas a body section, which is wider than the respective blade rootreceptacle in the placement area of the securing element and is free ofengagement of a retaining section when installed. The I-shaped securingelement is positioned between two U-shaped securing elements having thesame orientation, so that the opposite U-shaped securing element has awidened mating brace, so that three webs may be placed between its twowebs.

The respective form-fitting design can be improved and/or manufacturedmore simply if the retaining sections each have a catch nose withdimensional stability for reaching around the respective mating brace insome sections.

In a preferred method for axially securing rotor blades of a turboengine on a rotor disk, which are inserted with their roots into axialblade root receptacles on the rotor disk, axial securing elements areinserted into the blade root receptacles and are interconnected by atleast one form-fitting design. In this way, the securing elements areeach connected to a securing element on the opposite side and are thusmutually supported, so that there is a transfer of force to the outsidewithout any torque. Furthermore, a defined flow of force is ensured.

The mutual support can be further improved if the securing elements areconnected to one another by a mutual form-fitting design.

A preferred turbo engine has a bladed rotor disk, whose rotor blades areinserted into their blade root receptacles and are secured in the axialdirection by a restraint mechanism according to the invention.

Preferred exemplary embodiments of the invention are explained ingreater detail below on the basis of schematic diagrams.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 show a known axial means of securing a rotor blade on arotor;

FIG. 3 shows an assembly diagram of a pair of securing elements of arestraint mechanism according to the invention;

FIG. 4 shows a single diagram of an L-shaped axial securing element ofthe pair of securing elements;

FIG. 5 shows an exploded diagram of a pair of securing elements having aU-shaped securing element and a T-shaped securing element;

FIG. 6 shows an assembly diagram of a chain of securing elements of arestraint mechanism according to the invention;

FIG. 7 shows a single diagram of a U-shaped axial securing element ofthe chain of securing elements; and

FIG. 8 shows an exploded diagram of a pair of securing elements having alengthened U-shaped securing element and an I-shaped securing element.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 3 shows a securing element pair 20 of a restraint mechanismaccording to the invention for axially securing rotor blades (not shown)on a rotor disk (not shown). The root of each rotor blade is insertedinto an axial blade root receptacle and/or a rotor groove on the rotordisk. The rotor blades are secured radially in the rotor grooves by aform-fitting contour of the rotor grooves and roots. The restraintmechanism has a plurality of securing element pairs 20, in thisembodiment each having two identical axial securing elements 22, 22′,each forming mutually a form-fitting connection.

The securing elements 22, 22′ have, as in FIG. 4 for the securingelement 22, for example, a web 24, which has a retaining section 26 onthe end and a mating brace 28 on the end. The web 24 has a plate-typecontour and extends in the transverse direction y and/or has a widthcorresponding to the rotor groove in the placement area of the securingelement 22. The web 24 thus has mainly a width that is equal to ornarrower than the base of a groove.

The mating brace 28 is designed to be rigid and is arranged with anoffset in the vertical direction z with respect to the web 24. It has anelongated extent in the transverse direction y of the securing element22 and therefore has an elongated extent in the circumferentialdirection of the rotor disk. It is thus arranged at a distance from theweb 24 in the vertical direction z and is designed as a one-sided arm inthe exemplary embodiment shown here. It has an extent in the transversedirection y such that it bridges a neighboring rotor groove.

The retaining section 26 is plastically deformable and is set back atone end in comparison with the flanks of the web which are not labeledwith numbers. It is thus narrower than the rotor groove in the placementarea of the securing element 22. It can be converted from a shallowassembly position to the upright securing position shown here. Due tothe narrow design and the flat assembly position of the retainingsection 26, the rotor disk can be bladed before the securing elements 22are inserted into the rotor grooves because the retaining section 26 canbe pushed between the base of the groove and the blade roots. Theretaining section 26 preferably has a catch nose 30 to form a radiallyouter bordering face for a mating brace 28′ of a neighboring securingelement 22′ (see FIG. 3).

When installed on the rotor disk, two securing elements 22, 22′ are eachoriented so they are offset in relation to one another in the axialdirection x. With their webs 24, 24′ they each pass through a rotorgroove and are in contact with a front side face and/or a rear side faceof the rotor disk with their mating braces 28, 28′. The mating braces28, 28′ are offset in relation to one another in the circumferentialdirection of the rotor disk and they each bridge the rotor groove inwhich the web 24, 24′ of the opposite securing element 22, 22′ is placedand/or protrudes and/or out of which the retaining section 26, 26′ ofthe opposite securing element 22, 22′ protrudes. The retaining sections26, 26′ are shaped around the mating brace 28, 28′ of the oppositesecuring element 26, 26′ until the latter extend around the matingbraces 28, 28′ with their catch noses 30, 30′. The securing elements 22,22′ are then joined to one another mutually by a form-fitting design andthe rotor blades placed in these rotor grooves are releasably secured onthe rotor disk in the axial direction.

Due to the fact that the securing elements 22, 22′ are mutually secured,the rotor blades are double secured. If, for example, the retainingsection 26 is inadvertently released from the form-fitting design withthe mating brace 28′ or even breaks away from it, the respective rotorblade is still axially secured by the mating brace 28′ bridging therotor groove.

To also be able to cover the odd rotor blade numbers, a securing elementpair 32, illustrated in FIG. 5, is provided; three rotor blades can besecured on one rotor disk by this pair. This securing element pair 32consists of two different securing elements 34, 36, namely a T-shapedsecuring element 34 and a U-shaped securing element 36, which areinstalled opposite one another in the axial direction x.

The T-shaped securing element 34 has a web 24 which is placed at thecenter of a mating brace 28. The mating brace 28 thus extends on bothsides of the web 24 and more or less has two arm halves 38, 40. The armhalves 38, 40 have an extent in the transverse direction y, such that,when installed, they each bridge a neighboring rotor groove. At the end,the web 24 has a plastically deformable retaining section 26 with onecatch nose 30.

The securing element 36 is designed in a U-shaped design with two webs24′ spaced a distance apart from one another in the transverse directiony, each having a retaining section 26′ with a catch nose 30′ and beingconnected to one another via a mating brace 28′. The webs 24′ are spaceda distance apart from one another so that, when installed, they are notaccommodated in the respective neighboring rotor groove but instead inthe next-but-one rotor groove. In other words, when installed, an emptygroove is formed between the webs to receive the web 24 of the T-shapedsecuring element 34.

When installed on the rotor disk, the T-shaped securing element 34 andthe U-shaped securing element 36 are oriented oppositely from oneanother in the axial direction x. With their webs 24, 24′ they each sitin a rotor groove and are in contact at their mating braces 28, 28′ witha front side face and/or a rear side face of the rotor disk. TheT-shaped securing element 34 is placed with its web 24 in the emptygroove between the webs 24′ of the U-shaped securing element. Theretaining sections 26, 26′ are placed around the mating braces 28′, 28and/or the mating braces 28′ and the arm halves 38, 40 of the oppositesecuring element 36, 34, which are thereby connected to one another bytheir mutual form-fitting design.

Thus through a combination of the securing element pairs 20 consistingof the L-shaped securing elements 22, 22′ with the securing elementpairs 32 consisting of the T-shaped securing element 34 and the U-shapedsecuring element 36, all the rotor blade number variations can becovered.

FIG. 6 shows a securing element chain 42 of a restraint mechanismaccording to the invention. The securing element chain 42 ischaracterized in that a securing element 44′ is connected in a mutuallyform-fitting manner to both of its neighboring securing elements 44,44″, so that the restraint mechanism is closed in a ring shape aroundthe circumference of the rotor disk.

The securing elements 44, 44′, 44″ are identical and have a U-shapeddesign, as shown clearly by the securing element 44 in FIG. 7, forexample. They each have two webs 24 spaced a distance apart from oneanother in the transverse direction y, each of them having a retainingsection 26 with a catch nose 30 and connected to one another by a matingbrace 28. However, in contrast with the U-shaped securing element 36according to FIG. 5, the webs 24 with the securing elements 44, 44′, 44″are spaced so far apart from one another that, when installed, not justone empty groove but two free empty grooves each are formed betweenthem. The U-shaped securing elements 44, 44′, 44″ thus each extend overfour rotor blades.

As shown in FIG. 6, two of the U-shaped securing elements 44, 44″ arearranged side by side with the same orientation in the axial direction xwhen installed on the rotor disk. A third U-shaped securing element 44′is oriented in the axial direction x opposite the two U-shaped securingelements 44, 44″ which are oriented in the same way. The oppositesecuring element 44′ bridges with its mating brace 28′ two empty groovesin which the identically oriented securing elements 44, 44″ are eacharranged with one web 24, 24″. The retaining sections 26, 26′, 26″ areplaced in a form-fitting manner around the respective mating braces 28,28′, 28″ of the securing elements 44, 44′, 44″ and are thus connected tosame by a mutual form-fitting design. This placement is continued untilthe securing element chain 42 is closed.

For closing the chain, in the case of blade numbers not divisible byfour (4), a securing element pair 46 shown in FIG. 8 is installed one ormore times as a closure, because in the case of blade numbers notdivisible by four (4), at least one empty groove is formed between thesecuring elements 44, 44″ on the end and is aligned equally in the axialdirection x. The securing elements 44, 44″ on the end are thus spaced adistance apart from one another in the circumferential direction and canno longer be connected to an identical securing element 44′ because itsmating brace 28′ has a transverse extent y that is too short.

The securing element pair 46 thus comprises a U-shaped securing element48, whose two webs 24′ are spaced a distance apart from one another,such that its mating brace 28′ may extend over three empty grooves. TheU-shaped securing element 48 is thus broadened in the transversedirection y in comparison with the U-shaped securing elements 44, 44′,44″ according to FIGS. 6 and 7. The webs 24′ each have a retainingsection 26′ with a catch nose 30′ at the end.

To secure the rotor blade placed in the central empty groove, thesecuring element pair 46 has an approximately I-shaped securing element50. The I-shaped securing element 50 has a web 24″ which has a retainingsection 26′ with a catch groove 30′″. Instead of a mating brace 28, theI-shaped securing element 50 has a body section 52 at the end. The bodysection 52 is arranged with an offset in the vertical direction z incomparison with the web 24″ and has an extent on both sides of the web24″ such that, when installed, it is in contact with the side faces ofthe rotor disk.

When installed, the widened U shape securing element 48 is oriented inthe axial direction x opposite the U-shaped securing elements 44, 44″ atthe ends and bridges the empty groove. The retaining sections 26′, 26′of the widened U-shaped securing element 48 reach around the matingbraces 28, 28″ of the securing elements 44, 44″ on the ends. Theretaining sections 26, 26″ of the securing elements 44, 44″ on the endsreach around the mating brace 28′ of the widened U-shaped securingelement 48 with their catch noses 30, 30″. The securing elements 44,44″, 48 are now situated in mutual form-fitting engagement. For axiallysecuring the rotor blade arranged in the empty groove, the I-shapedsecuring element 50 is inserted into the empty groove opposite thewidened U-shaped securing element 48. With its body section 52, it isthen in contact at the sides with the empty groove on the side faces ofthe rotor disk, and it extends around the mating brace 28′ of theU-shaped securing element 48 in a form-fitting manner with its retainingsection 26′″ and its catch nose 30′″.

The securing elements 22, 34, 36, 44, 48, 50 are each made of a metallicmaterial, i.e., a metal alloy. The mating braces 28 are preferablycurved according to the rotor disk in the transverse direction y of thesecuring elements and thus also in the circumferential direction of therestraint mechanism and/or the rotor disk.

The present invention discloses a restraint mechanism for rotor bladesof a turbo engine on a rotor disk, which has blade root receptacles forradial guidance of the rotor blades, having a plurality of axialsecuring elements, each having at least one web for positioning in oneblade root receptacle such that each web has a retaining section at theend for establishing a form-fitting design to a mating brace of adifferent axial securing element, as well as a method for axiallysecuring rotor blades on a rotor disk and a turbo engine.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

List of Reference Numerals

-   1 rotor blade-   2 root-   4 groove-   6 rotor disk-   8 securing element-   10 web-   12 securing section-   14 securing section-   16 front disk face-   18 rear disk face-   20 securing element pair-   22, 22′ securing element-   24, 24′, 24″ web-   26, 26′, 26″ retaining section-   28, 28′, 28″ mating brace-   30, 30′, 30″ catch nose-   32 securing element pair-   34 securing element-   36 securing element-   38 arm half-   40 arm half-   42 securing element chain-   44, 44′, 44″ securing element-   46 securing element pair-   48 securing element-   50 securing element-   52 body section-   x axial direction-   y transverse direction-   z vertical direction

What is claimed is:
 1. A restraint mechanism for rotor blades of a turboengine on a rotor disk, comprising: a plurality of axial securingelements, wherein each of the plurality of axial securing elements hasat least one web for positioning in a respective blade root receptacleof the rotor disk, wherein the at least one web has a retaining sectionat a first end and a mating brace at a second end, and wherein theretaining section of one of the plurality of axial securing elementsconnects to the mating brace of an opposite one of the plurality ofaxial securing elements.
 2. The restraint mechanism according to claim1, wherein the retaining section is narrower than the respective bladeroot receptacle and has both an installation position and a securingposition.
 3. The restraint mechanism according to claim 1, wherein themating brace is offset in a vertical direction of the axial securingelement and has an elongated shape extending in a transverse directionof the axial securing element, and wherein the mating brace has anextent such that, when installed, the mating brace extends over at leastone neighboring blade root receptacle.
 4. The restraint mechanismaccording to claim 3, wherein two of the plurality of axial securingelements form a securing element pair and wherein the respective matingbraces of the two axial securing elements extend in the transversedirection on one end of the respective axial securing element.
 5. Therestraint mechanism according to claim 3, wherein two of the pluralityof axial securing elements form a securing element pair, wherein themating brace of a first of the two axial securing elements extends onboth sides of the respective at least one web, and wherein the matingbrace of a second of the two axial securing elements extends between therespective at least one web and a second web of the second of the twoaxial securing elements.
 6. The restraint mechanism according to claim3, wherein at least one of the plurality of axial securing elements hasa second web, wherein the respective mating brace of the at least one ofthe plurality of axial securing elements extends between the at leastone web and the second web, and wherein the respective at least one webof two opposite axial securing elements of the plurality of axialsecuring elements are disposed between the at least one web and thesecond web of the at least one of the plurality of axial securingelements.
 7. The restraint mechanism according to claim 6, wherein atleast one of the plurality of axial securing elements is an I-shapedaxial securing element, wherein the I-shaped axial securing element doesnot have a mating brace and has a body section that is wider than arespective blade root, and wherein the I-shaped axial securing elementis disposed between the at least one web and the second web of the atleast one of the plurality of axial securing elements.
 8. The restraintmechanism according to claim 1, wherein the retaining section has acatch nose and wherein the catch nose connects to the mating brace ofthe opposite one of the plurality of axial securing elements.
 9. Amethod for axially securing rotor blades on a rotor disk of a turboengine, comprising the steps of: inserting respective blade roots of therotor blades into respective axial blade root receptacles of the rotordisk; and inserting securing elements which are connected to one anotherby at least a form-fitting connection into the blade root receptacles.10. The method according to claim 9, wherein the securing elements areconnected to one another by a mutual form-fitting design.
 11. A turboengine, comprising: a bladed rotor disk, wherein blades of the bladedrotor disk are secured axially by a restraint mechanism according toclaim
 1. 12. A restraint mechanism for rotor blades of a turbo engine ona rotor disk, comprising: a first axial securing element, wherein thefirst axial securing element has a first web, a first retaining sectionat a first end of the first web, and a first mating brace at a secondend of the first web, wherein the first web is positioned in a firstblade root receptacle of the rotor disk, and wherein the first retainingsection is disposed on a first side of the rotor disk and the firstmating brace is disposed on a second side of the rotor disk; and asecond axial securing element, wherein the second axial securing elementhas a second web, a second retaining section at a first end of thesecond web, and a second mating brace at a second end of the second web,wherein the second web is positioned in a second blade root receptacleof the rotor disk, and wherein the second retaining section is disposedon the second side of the rotor disk and the second mating brace isdisposed on the first side of the rotor disk; wherein the first bladeroot receptacle is adjacent to the second blade root receptacle; whereinthe first side of the rotor disk is opposite from the second side of therotor disk; wherein the first retaining section of the first axialsecuring element disposed on the first side of the rotor disk isconnected to the second mating brace of the second axial securingelement disposed on the first side of the rotor disk; and wherein thesecond retaining section of the second axial securing element disposedon the second side of the rotor disk is connected to the first matingbrace of the first axial securing element disposed on the second side ofthe rotor disk.